Multioffice telephone system



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Patented Aug. 9, 1927.

UNITED STATES JOHN E. Gunman,

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS,

OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

A CORPORATION OF DELAWARE.

mun'rrorrrca TELEPHONE SYSTEM.

, i L Application flle'd December 28, 1922, Serial No. 608,741. Renewed December 16, 1926.

The present invention relates in general to multi-oflice telephone systems of the automatic type, and the broad general object of the invention is the provision of novel and improved trunking arrangements for a system of this character whereby the inter-oflice griunking facilities are rendered more flexie e.

More specifically, the present invention comprehends a new and improved director of simplified construction for increasing the efficiency and flexibility of the inter-oflice trunking in automatic multi-office systems using step by stem switches of the Strowger type. It is well known that in multi-oflice systems of this type the designation of the ofiice or the ofiice name bears a definite relation to the geographical districts. The inventionallows the names or the numbers of ofiic'es in a multi-ofiice system to be assigned without regard to their geographical districts. That is. in a multi-ofiice system comprising a number of districts, oflices having conflictin names ma be located in difierent districts, if desired, instead of it being necessary to locate them in the same geographical district, as is the usual practice. The invention also provides means for routing calls thru a plurality of ofiices in series, which may or may not have any relation to the numerical designation of the desired exin order to increase the efficiency of the inter-office trunk groups. This arrangement is commonly called tandem trunking.

Another feature of the invention provides means for eliminating certain .switches in the connection when it is not necessary for the call to be extended through a plurality of exchanges.

Another feature of the invention provides means for releasing the director after the office code has been set up provided the controlling impulses of the director catch up -with the dialing operations of the calling subscriber. This arrangement allows the director to be released and to revert to common' use. In addition, by this arrangement the number of digits in subscribers numbers do not have to be uniform, and yet the same number of register switches sufiice in all cases.

' A further feature of the invention relates to an arrangement of controlling circuits so that the registering switches of the director may be used over and over again, thus lessening the number of register switches necessary for registering subscribers directory numbers.

It is especially desirable'to accomplish the above result of enabling oflice designations to be assigned without regard to the geographical location of the offices, in view of the fact that many large manual multi-oflice systems are being changed to automatic operation and in View of the fact that when such changes are made, it is both desirable and advisable to retain the old manual exchange names as well as the subscribers numbers in order to avoid undue confusion. Following this scheme, when the automatic system is installed, the calling devices have letter combinations in the ditionto the usual digits, so that the calls maybe routed to the desired offices in accordance with the ofiice names, that is, the

first two or three letters of each office name,

may be dialed by the calling subscriber, these letters forming part of the directory numbers. In the changing of a large multi-office manual system to automatic it is usually necessary to employ the first three letters of the exchange names as part of the directory number of the subscribers, in order to secure proper selection of the exchanges, the re maining portion of the number consisting of four numerals. It' will at once be appreciated .that, as in majority of cases the manual exchange names have been promiscuously assigned, situations are encountered where there isconfliction in the first one or two letters in the names of the exchanges in difi'erent'districts, the letters of these names being in the same finger holes on the calling device dial, and it consequently becomes necessary to provide trunking arrangements of the kind indicated above to complete connections to the various exchanges of the system. The present invention handles these trunking connections quite economically.

In addition to the above, there are a number of other objects-0f the invention,'all of which will be described hereinafter with reffinger holes in aderence to the accompanying drawings forming a part of this specification.

General description of drawings.

Referring now to the drawings comprising Figs. 1-22, inclusive, Fig. 1 is a map of 

